复碱化混凝土孔溶液的pH值

碳化混凝土的复碱化是用碳酸钙缓冲溶液浸渍混凝土的电化学过程，目的是使混凝土孔溶液的pH值稳定在l0以上，从而防止混凝土的进一步碳化。然而，该方法的实际应用表明：虽然孔溶液中已明显含有足量的碱(Na^ ，K^ ，Li^ )，但pH值仍降到l0以下。本文通过试验提出了一个用以解释pH值随时间降低的假说，结果表明：由于混凝土孔溶液中存在溶解的硫酸盐，因此单纯提高孔溶液的碱离子(碳酸盐)相对含量，不能确保其pH值高于l0、用提出的化学机理可解释混凝土电化学复碱化技术实际应用中观察到的现象，但是，由于混凝土孔溶液中溶解离子相互作用十分复杂，目前还不能在复碱化技术中对其加以考虑，因此复碱化技术尚不能被进一步推荐应用。

Evolution of pH Value of the Pore Solution after Realkalisation of Carbonated Concrete

Method for realkalisation of carbonated concrete is based on the electrochemicalprocesses. In order to increase the pH value of pore solution the concrete is impregnated withalkali carbonates solutions. These buffer solutions should stabilize the pH value of pore solu-tion at a level higher than 10. However, analyses of impregnated concrete in practice showthat the pH value drops to values below 10 although sufficient alkali (Na+ , K+ , Li+ ) con-centration was available in pore solution. Experiments were carried out to confirm a hypothe-sis to explain the time-dependent decrease of the pH value. It is concluded that in the pres-ence of dissolved sulfates even a comparatively high content of alkali carbonates is not suffi-cient to maintain pH value higher than 10. The chemical mechanisms suggested in this paperare used to explain observations of practical applications. The complex interactions of dis-solved ions in pore solution have hardly been taken into consideration of the development ofnew technologies for realkalisation up to now. For this reason, the methods for realkalisationof carbonated concrete as discussed in this paper cannot be recommended.